The invention concerns a contact element for electrical contact of printed circuit boards to a front module rail of a module support structure or a module support structure housing means. A contact element of this kind is mounted to the forward region of a guide rail which has a guide groove for insertion of a printed circuit board and which can be inserted into at least one positioning hole of the module rail. It comprises at least one leaf spring elastically seated on the inserted printed circuit board, a contact means effecting an electrical contact to the module rail and a connecting piece between the leaf spring and the contact means.
Guide rails for the insertion of printed circuit boards, having electrical or electronic components, into module support structures or into module support structure housing means are usually made from plastic. As long as a printed circuit board is not inserted in the rear plug connector of the module support structure, interfering potential differences between the printed circuit board and the module support structure, occurring e.g. due to electrostatic charge-up of the printed circuit board, cannot be compensated for due to the non-conducting plastic of the guide rail. However, the printed circuit boards first come into electrical contact with the connector plug of the module support structure when they are nearly completely inserted. Moreover, an uncontrolled potential compensation at the plug connector is undesirable, since sensitive electronic components could thereby be damaged.
In order to avoid the above mentioned problem when inserting printed circuit boards in guide rails of module support structures, contact elements are mounted to the front region of the guide rails to establish electrical contact between the inserted printed circuit board and a front module rail. These contact elements usually consist essentially of a leaf spring and a contact means, connected via a connecting piece. When inserting the printed circuit board, the leaf spring resiliently seats on potential compensation leads in the printed circuit board and the contact means seats on the module rail. In many cases, an advance potential compensation between a printed circuit board and a front module rail, and thereby the module support structure, is thereby already established when the printed circuit board is inserted. No potential difference is therefore present between the printed circuit board and the module support structure when contact is made with the plug connector.
A contact element of the above mentioned kind is known in the art from DE 296 02 428 U1. The contact element described therein is divided into a clamping region and a holding region, wherein the clamping region comprises two leaf springs between which a printed circuit board is inserted and the holding region is snapped onto the front lower module rail of a module support structure.
Known in the art from EP 0 399 091 B1 is a contact element of the above mentioned kind. The contact element described herein has two leaf springs which seat, in the form of a U-shaped clip, in the guide groove of a guide rail as well as a contact means which is connected to the leaf springs via a connecting member engaging over the side legs of the guide rail and achieves electrical contact with the module rail via a formed contact spike pressed onto the surface of the module rail.
The contact elements of prior art have the common feature that the contacting with the module rail is unsatisfactory, at least when the module rail is made from aluminum and has an anodized surface. Since anodized aluminum surfaces are durable and insensitive, profile structured rails, normally made from aluminum, having anodized surfaces are nevertheless preferred.